Advanced video coding techniques are important for multimedia storage and transmission. For this reason, many video coding standards have been standardized. H.264 is the latest video coding standard. H.264/AVC standard jointly developed by ISO and ITU-T—Joint Video Team (JVT), also known as MPEG-4 Part 10 and H.264 in the H.26x serial standards, has substantially outperformed the previous video coding standards by utilizing a variety of temporal and spatial predictions. Rate control is an important technique although it does not belong to the normative part in video coding standards. However, without rate control any video coding scheme would be practically useless in many applications because the client buffer may often under-flow and over-flow when a channel used to deliver the compressed stream is of constant bandwidth. Therefore, every video coding standard has its own rate control technique, for example, TM5 for MPEG-2 and TMN8 for H.263.
RDO is one of important video coding techniques. It is used to select optimal motion vectors an optimal coding mode for every macroblock. Yet the RDO used in H.264 test model makes it difficult to adopt the existing rate control techniques. Because rate control usually requires a pre-determined set of motion vectors and coding modes to select the quantization parameter, whereas RDO requires a pre-determined quantization parameter to select motion vectors and coding modes. On the other hand, as the complexity ratio between coded frame, the bit allocation model and adaptive quantization scheme should also be improved. The invention is a method and apparatus for rate distortion optimization based rate control. The invention can be used for video streaming, transmission, and storage coding.